Methods of in vitro analysis using time-domain NMR spectroscopy
View Patent ↗An in vitro method of determining an analyte concentration of a sample includes placing the sample into a low-field, bench-top time-domain nuclear magnetic resonance (TD-NMR) spectrometer. The NMR spectrometer is tuned to measure a selected type of atom. A magnetic field is applied to the sample using a fixed, permanent magnet. At least one 90 degree radio-frequency pulse is applied to the sample. The radio-frequency pulse is generally perpendicular to the magnetic field. The 90 degree radio-frequency pulse is removed from the sample so as to produce a decaying NMR signal. The decaying NMR signal is measured at a plurality of times while applying a plurality of 180 degree refocusing radio-frequency pulses to the sample. The analyte concentration is calculated from the plurality of measurements associated with the decaying NMR signal and a selected model.
1. An in vitro method of determining an analyte concentration of a sample, the method comprising the acts of:
placing the sample into a low-field, bench-top time-domain nuclear magnetic resonance (TD-NMR) spectrometer, the NMR spectrometer being tuned to measure a selected type of atom;
applying a magnetic field to the sample using a fixed, permanent magnet;
applying at least one 90 degree radio-frequency pulse to the sample, the radio-frequency pulse being generally perpendicular to the magnetic field;
removing the 90 degree radio-frequency pulse from the sample so as to produce a decaying NMR signal;
measuring the decaying NMR signal at a plurality of times while applying a plurality of 180 degree refocusing radio-frequency pulses to the sample; and
calculating the analyte concentration from the plurality of measurements associated with the decaying NMR signal and a selected model.
2. The method of claim 1 , wherein the sample is a body fluid.
3. The method of claim 2 , wherein the sample is a blood plasma sample.
4. The method of claim 2 , wherein the sample is a blood serum sample.
5. The method of claim 2 , wherein the sample is a urine sample.
6. The method of claim 1 , wherein the analyte is selected from the group consisting of glucose, cholesterol, triglycerides, albumin, blood urea nitrogen, alkaline phosphastase, and creatinine.
7. The method of claim 1 , wherein the method is a reagentless method.
8. The method of claim 1 , wherein the method includes adding an NMR contrast agent to the sample to enhance the detection of the selected analyte.
9. The method of claim 1 , wherein the selected type of atom is hydrogen, fluoride, or phosphorous.
10. The method of claim 1 , wherein the NMR spectrometer includes a permanent magnet less than about 1.4 tesla in the absence of hardware or electronics for locking or shimming.
11. The method of claim 1 , wherein the plurality of measurements is all of the measurements in the absence of processing.
12. The method of claim 1 , wherein the plurality of measurements is a subset of all of the measurements in the absence of processing.
13. The method of claim 1 , wherein the plurality of measurements includes data that is representative of the original measurements after preprocessing for smoothing.
14. The method of claim 1 , wherein the plurality of measurements includes a subset of data that is representative of the original measurements after preprocessing for smoothing.
15. The method of claim 1 , wherein the plurality of measurements includes data that is representative of the original measurements after preprocessing by fitting to a function.
16. The method of claim 15 , wherein the plurality of measurements includes a subset of data that is representative of the original measurements after preprocessing by fitting to a function.
17. An in vitro method of determining an analyte concentration of a sample, the method comprising the acts of:
placing the sample into a low-field, bench-top time-domain nuclear magnetic resonance (TD-NMR) spectrometer, the NMR spectrometer being tuned to measure a selected type of atom;
applying a magnetic field to the sample using a fixed, permanent magnet;
applying at least one 90 degree radio-frequency pulse to the sample, the radio-frequency pulse being generally perpendicular to the magnetic field;
removing the 90 degree radio-frequency pulse from the sample so as to produce a decaying NMR signal;
measuring the decaying NMR signal at a plurality of times while applying a plurality of 180 degree refocusing radio-frequency pulses to the sample; and
calculating the analyte concentration from the plurality of measurements associated with the decaying NMR signal and a selected model,
wherein the selected model is a multivariate calibration model.
18. The method of claim 17 , wherein the multivariate calibration model uses a chemometric technique.
19. The method of claim 18 , wherein the chemometric technique uses partial least squares (PLS).
20. The method of claim 18 , wherein the chemometric technique uses principal components regression (PCR).